1. Each Contracting State shall have and maintain legislation prohibiting, subject to penalties, any forgery, unauthorised alteration or misuse of the Common Control Mark or of the marks of the authorised assay offices which have been notified in accordance with paragraph 3 of Article 5, and any unauthorised alteration to the article or alteration or obliteration of the fineness mark or responsibility mark after the Common Control Mark has been applied.
2. Each Contracting State undertakes to institute proceedings under such legislation when sufficient evidence of forgery or misuse of the Common Control Mark or marks of the authorised assay offices, or unauthorised alteration to the article or alteration or obliteration of the fineness mark or responsibility mark after the Common Control Mark has been applied is discovered or brought to its attention by another Contracting State or, where more appropriate, to take other suitable action.